At first I would like to tell you the recommendation of the restore operation.

For S-Series, K2, and Cloud PBX the mandatory conditions are:

Same Firmware Version

Extension Capacity should be equal to or lower than restored unit.

Therefore restore S20 (30.10.0.34) backup file on S100 (30.10.0.34) is safe. In the contrary, it is not safe. Capacity issue happens like the only 20 extensions would display.

For U-Series, the mandatory conditions are:

Same Model

Same Firmware Version

While for U100/U200, U500/U510/U520 are exceptions based on the same firmware version. You would need obey the rule: Extension and Trunk Capacity should be equal to or lower than restored unit.

So restore U100 (15.19.0.48) backup file on U200 (15.19.0.48) is safe. In the contrary, it is not safe. Capacity issue happens like the only 100 extensions would display.

Also these restore operations are safe: from U500 (14.19.0.48) to U510/U520 (14.19.0.48), from U510 (14.19.0.48) to U520 (14.19.0.48).

For Gateways, the mandatory conditions are:

Same Model

Same Firmware Version

Same Hardware Version

It's special for gateways that we developed different hardware versions for the products lines. To distinguish them. The best method is the firmware version start number. See the list:

TGv1: 5.X.X.X

TGv2: 5X.X.X.X

TGv3: 91.X.X.X

TA FXS v1/V2: 40.X.X.X, 41.X.X.X

TA FXS v3: 47.X.X.X

TBv1: 6.X.X.X

TBv2: 18.X.X.X

Finally let's check out the questions in the beginning.

"Could I restore the old backup into the new version device?"

No, because the firmware version is different. Sometimes might work, but it is not that recommended. As it's not very sure which database tables might be different. While restore the new version backup for old version device. It's absolutely not working.

"Could I restore the backup file from U100 for S100?"

The answer is NO, as they are different products. Database structure are totally different.

"Could I restore the backup file from S20 for S100 or vice versa?"

From S20 to S100 is safe, but it is not safe for the contrary.

"Could I restore the backup file from TGv2 for TGv3?"

NO, the hardware version is different.

Tips

Restore high version file for low version device.

Please upgrade the low version device to the same version. Then perform restore.

Restore low version file for high version device.

Please downgrade the high version device to the same version and check reset option. Then perform restore.